Gene therapy has vast potential for treating and potentially curing a wide variety of disorders, in particular in a number of retinal diseases including glaucoma, age-related macular degeneration, and photoreceptor diseases. However, gene delivery technologies require significant improvements in cellular targeting, efficiency, and safety before promising findings in animal studies can be translated to the clinic. In particular, for retinal gene therapy it would be highly advantageous to transduce a single cell type that spans the entire retina for the delivery and secretion of a general neuroprotective factor throughout the retina to protect numerous populations of neurons that are affected by different retinal diseases, from retinal ganglion cells to photoreceptors. In addition, ideally this single cell type should be accessible from an intravitreal injection, as subretinal injections are more invasive and disruptive to the retina. Unfortunately, there is no vector capable of efficiently infecting the cell type that meets these needs, Muller glia. Vectors based on adeno-associated virus (AAV) have proven themselves to be highly promising in numerous retinal disease models, but they are also unfortunately incapable of Muller cell infection. We have developed novel directed evolution technology to generate new mutants of AAV with new properties, including altered receptor binding, and we propose to evolve variants capable of efficient Muller cell transduction. In parallel, the basic mechanisms of AAV transduction of Muller cells will be explored. Finally, results will be translated to photoreceptor disease model. The novel approaches developed in this work will have general impact for the molecular engineering of enhanced viral gene delivery vehicles for a number of retinal diseases. [unreadable] [unreadable] [unreadable]